For example, preparative separation/purification systems including a liquid chromatograph are used in the pharmaceutical industry to collect samples of a variety of chemically synthesized compounds in order to store those samples into a library or analyze them in more detail. Conventional examples of the preparative separation/purification systems are disclosed in Japanese Unexamined Patent Application Publication Nos. H02-122260, 2003-149217 and other documents.
In these conventional apparatuses, objective components (compounds) in a sample solution are temporally separated by a liquid chromatograph. The separated objective components are then respectively introduced into different trap columns and temporarily captured therein. Subsequently, a solvent is supplied into each trap column to quickly elute the component from the trap column and collect it in a container. Thus, a plurality of solutions each containing one objective component at a high concentration are respectively collected in a plurality of containers. These separately collected solutions are then subjected to a vaporizing and drying process to remove the solvent and collect the objective components in solid forms. The vaporizing and drying process normally includes heating the collected solutions or centrifuging them under vacuum.
In this preparative separation/purification process, it has been desired in some cases that a component contained in the sample solution by a relatively large amount should be accurately separated into equal aliquots and collected in the form of small solids rather than a single mass. This requirement cannot be met, for example, by separating the eluate into equal volumes in the preparative separation process of the eluate containing the objective component; what is necessary is to control the volume of each aliquot of the eluate so that every aliquot contains the same amount of the objective component.
Japanese Patent No. 3864876 discloses a preparative LC system designed for separating an eluate into a plurality of containers in such a manner that every separate sample contains the same amount of the objective component. This preparative LC system monitors the height of peaks appearing on a chromatogram and controls the sampling operation so that the amount of the eluate to be collected in the container will be decreased for higher peaks. Controlling the volume of the aliquot of the eluate according to the peak height will work if the peak shape is comparatively normal and clear, but will not yield good results if the peak shape is abnormal and distorted. For example, if the curve on the anterior side of the peak top is not monotonically increasing or the curve on the posterior side of the peak top is not monotonically decreasing, the amounts of the objective component in the separately sampled solutions are likely to be significantly dispersed.
The preparative separation apparatus described in Japanese Patent No. 3864876 uses test tubes or similar containers to collect the sample. In this case, if the sample has a low concentration of the objective component, it is necessary to collect a large amount of the eluate in the container, which possibly causes the eluate to exceed the capacity of the container and overflow.
The present invention has been developed in view of the previously described problems. Its first objective is to provide a preparative LC system capable of more accurately separating an objective component into equal aliquots, regardless of the peak shape, without causing an overflow or other problems of an eluate even if the concentration of the objective component is low. The second objective of the present invention is to provide a preparative separation/purification method capable accurately separating an objective component in a sample solution into equal aliquots and collecting them in solid forms.